"Had you donated that $8 million you spent fighting Proposition F directly to the public libraries you love so much, that could have made a bigger difference. Oh well. Hindsight is 20/20!" said San Francisco State University professor Martha Kenney in her Facebook post.

Another ad, posted on a city bus stop, suggested that the city should be feeding expired parking meters. (We're not sure why.)

"The intent was to show the hotel tax contribution from our hosts and guests, which is roughly $1 million per month. It was the wrong tone and we apologize to anyone who was offended. These ads are being taken down immediately," said Airbnb spokesman Christopher Nulty.

Among the ads' suggestions for what to do with the money Airbnb pays in hotel taxes:

"Please use $12 million in hotel taxes to feed all expired parking meters."

"We hope you use some of the $12 million in hotel taxes to put escalators on all the hills."

"We hope you use some of the $12 million in hotel taxes to keep the library open later."